Reversing pawl mechanism



March 18, 1969 I v, KOUDELKA 3,433,329

REVERSING PAWL MECHANISM Filed April 5, 1967 V Sheet 1 of 2 aqy.

INVENTOR. Mad/Mfr fl oua/e/(a 3,433,329 REVERSING PAWL MECHANISM Vladimir Koudelka, Krivoklat, Czechoslovakia, assignor to Naradi, narodni podnik, Prague, Czechoslovakia Filed Apr. 5, 1967, Ser. No. 629,061 US. Cl. 188-822 Int. Cl. F16d 63/00; GtlSg 5/06, 1/00 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to new and useful improvements in reversing pawl mechanisms which arrest rotation of an associated ratchet selectively in one direction or the other.

Conventional pawl and ratchet mechanisms belong generally in two categories, one of these being a non-reversible type where a single pawl arrests rotation of the ratchet in only one predetermined direction. The other is a reversible type, the most common version of which includes two pawls operatively connected by linkage so that either pawl may engage the ratchet while the other is disengaged therefrom, depending upon the direction of rotation which is to be arrested. The nonreversible type of mechanism obviously does not facilitate rotation selectively in opposite directions, while the reversible type with its two pawls is unduly complicated, expensive to manufacture, difficult to adjust, and likely to get out of order, particularly where the mechanism is subjected to shocks and vibrations, as for example in rock drills, pneumatic hammers, and the like.

The principal object of the invention is to eliminate the disadvantages of conventional mechanisms as above outlined, this being attained by an improved mechanism which utilizes a single reversible pawl in conjunction with a ratchet. Although several such pawls may be provided at circumferentially spaced points around the ratchet, each one of them is capable to individually perform its function in arresting rotation of the ratchet selectively in one direction or the other, by simply partially rotating the pawl in the body or housing of the mechanism so as to change the attitude of the pawl relative to the ratchet.

An important feature of the invention resides in the provision of simple and highly effective means for partially rotating the pawl and thereby reversing the action thereof as desired. These means include a partially rotatable actuating disc which is positioned in the body or housing of the mechanism coaxially with the ratchet and accommodates a radially slidable pin, the latter being yieldably biased outwardly against the pawl so that the attitude of the pawl relative to the ratchet may be reversed 3,433,329 Patented Mar. 18, 1969 by partially rotating the actuating disc in the mechanism body. Another important feature of the invention resides in that the aforementioned pin carried by the actuating disc may be yieldably biased against the pawl either by spring pressure or by fluid pressure, and that in either instance, the arrangement is such that the yieldably biased pin serves not only to reverse the attitude of the pawl upon actuation of the associated disc, but also to hold the pawl in operative engagement with the ratchet while permitting normal skipping of the pawl over the ratchet teeth when the ratchet is rotated in a desired direction.

With the foregoing more important object and features in view and such other objects and features as may become apparent as this specification proceeds, the invention will be understood from the following description taken in conjunction with the accompanying drawings, wherein like characters of reference are used to designate like parts and wherein:

FIG. 1 is a fragmentary sectional view of the improved mechanism, taken along the axis of ratchet rotation;

FIG. 2 is a fragmentary cross-sectional view, taken substantially in the plane of the line 2-2 in FIG. 1;

FIG. 3 is an enlarged fragmentary sectional detail, taken substantially in the plane of the line 3-3 in FIG. 1;

FIG. 4 is an enlarged fragmentary sectional detail, taken substantially in the plane of the line 44 in FIG. 1;

FIG. 5 is a view similar to that in FIG. 3 but showing the pawl in a reversed position;

FIG. 6 is a view similar to that in FIG. 4 but showing the pawl in the reversed position;

FIG. 7 is a perspective view of one of the pawls;

'FIG. 8 is a fragmentary sectional detail, taken substantially in the plane of the line 8-8 in FIG. 1; and

FIG. 9 is a view similar to that in FIG. 2 but showing a modified embodiment of the invention.

Referring now to the accompanying drawings in detail, the pawl and ratchet mechanism of the invention is contained in a body or housing consisting of a central hollow section 1 and side sections 4, 5 held in assembled relationship by suitable screws 2, 3. The hollow central section 1 provides a chamber which accommodates a rotatable ratchet 7, the latter having journals 6, 6a rotatable in the body sections 5 and 4, respectively. The peripheral wall of the chamber 1a in the body section 1 is provided at circumferentially spaced points with pawl-receiving recesses 8 which are in the form of a partial cylinder extending in parallel to the axis of rotation of the ratchet 7. Each one of the recesses 8 provides a seat for a partially cylindrical pawl 9 which is substantially complemental in shape to its associated recess. Although only one such pawl is capable of performing its intended function with the ratchet, several pawls may be provided around the ratchet periphery, as already indicated. Since the arrangement of them all is the same, a description of one will suflice for all.

Each pawl 9 has a concave surface 921 oriented toward the ratchet 7 and also has a pair of longitudinal edge portions 9b and as is best shown in FIG. 7. These edge portions are selectively engageable with the ratchet teeth 7a upon partial rotation of the pawl in the recess 8. In other words, if the pawl is rotated in the recess to the position shown in FIG. 3, the edge 9c of the pawl will engage the ratchet teeth 7a. On the other hand, the pawl may be rotated to the position shown in FIG. 5 wherein the edge 9b of the pawl engages the ratchet teeth.

A pawl actuating disc is positioned on the ratchet journal 6a inside the chamber 1a and is partially rotatable in the chamber, independently of rotation of the ratchet 7. The disc 10 has secured thereto an actuating bar 12 which projects outwardly through an arcuate slot 26 formed in the body section 4, the bar 12 being movable within the limits of the slot 26 so as to correspondingly limit the extent of partial rotation of the disc 10 in the chamber In.

The disc 10 is provided with a plurality of radial cavities 10a each accommodating a slidable pin 11. Each pin has a convex outer end engageable with the concave surface 9a of one of the pawls 9, it being understood that as many pins are provided as there are pawls. Each pin is yieldably biased radially outwardly into engagement with the surface 9a of the associated pawl, either by fluid pressure or by spring pressure, as Will be hereinafter described.

Reference is now drawn to FIGS. 4- and 6 where, in FIG. 4, the outwardly biased pin 11 has its convex end 11a in engagement with the concave surface of the pawl 9 adjacent the pawl edge 911, while the pawl edge 90 engages the ratchet teeth 7a as in FIG. 3. In this position the actuating bar 12 of the disc 10 is at one end of the slot 26, as for example in the position 12a shown in FIG. 2. Now if the bar 12 is moved to the opposite end of the slot 26, as to the position 1212 in FIG. 2, the disc 19 is partially rotated in the chamber In, which causes the pins 11 to move transversely across the concave surface 9a of the pawls 9 from the edge 9b to the edge 90. By this action the pawls are partially rotated in their recesses 8 to the position shown in FIGS. 5 and 6, wherein the ratchet teeth are engaged by the pawl edges 91) while the edges 90 are disengaged from the ratchet.

It will be understood that the pawls 9 are of such length as to span the combined axial dimension or thickness of the ratchet 7 and the disc 10 as shown in FIG. 1. The periphery of the disc 10 is provided at opposite sides of each pin 11 with notches 13a, 13b to provide clearance for the pawl edges 9b, 9c when either of these edges is brought into engagement with the ratchet teeth 7a. Preferably, the notches 13a, 13b are larger than the spaces 14 between the ratchet teeth, so that suflicient clearance for the pawl edges is obtained. Also, to provide clearance for the pins 11 in their radially projected positions, the body section 1 is relieved at the opposite sides of each recess 8 as indicated at 15 in FIG. 2.

As already indicated, the pins 11 may be biased outwardly into engagement with the pawls 9 either by fluid pressure or by spring pressure. In the fluid pressure arrangement, the inner ends of the cavities 10a in the disc 10 communicate through ducts 16 with an annular groove 17 formed in the disc 10 around the ratchet journal 6a, and a further duct 18 communicates the groove 17 with an annular space 19 which exists at the center of the ratchet and journal unit 6, 6a, 7, around a tube 20 fitted centrally into that unit. One end of the annular space 19 in the journal 6a is packed as indicated at 19a, while its other end in the journal 6 communicates through a duct 21 with an annular groove 22 formed in the body section 5 around the journal 6. The body section 5 in turn has a duct 23 communicating with the annular groove 22, thus forming continuous passage means whereby fluid under pressure, such as compressed air, for example, admitted through the duct 23 may be delivered into the disc cavities 10a in order to bias the pins 11 outwardly against the pawls 9, notwithstanding rotation of the ratchet unit 6, 6a, 7 and of the disc 10 relative to the mechanism body 1, 4, 5.

It may be noted that the fit of the various parts, for example, that of the pins 11 in the cavities 10a, is sufficiently loose to facilitate free sliding action of the pins as well as some amount of leakage of fluid past the pins, which may be desirable when the pins are retracted against fluid pressure during normal skipping action of the pawls 9 over the ratchet teeth 7a, as hereinafter mentioned. Nevertheless, the fluid pressure in the cavities 10a is such as to yieldably bias the pins 11 to their projected positions against the pawls 9. Any fluid escaping past the pins 11 into the chamber 1a is discharged to the atmosphere, as through a vent 24 provided in the body section 1 as shown in FIG. 1.

The modified embodiment of the invention shown in FIG. 9 omits all the ducts, passages, et cetera of the fluid pressurized system and utilizes simple compression springs 25 which are positioned in the cavities 10a to resiliently bias the pins 11 outwardly into engagement with the pawls 9. Otherwise the construction of the modified embodiment is the same as already described.

In operation, the pins 11 are yieldably biased, either by fluid pressure or by spring pressure, against the pawls 9 and when the bar 12 of the actuating disc 10 is set so that the pins 11 cause the pawls 9 to assume the attitude shown in FIGS. 3 and 4, the edge 9c of the pawls operatively engages the ratchet teeth 7a, as already mentioned. In this attitude of the pawls, the ratchet 7 may rotate in the direction of the arrow P in FIG. 3, and during such rotation the pawl edge 9c will skip over the ratchet teeth against the yieldable biasing action of the pin 11 directed on the opposite edge portion 9b of the pawl. However, rotation of the ratchet in a direction opposite to the arrow P will be arrested by the pawl edge 90, as will be clearly apparent. On the other hand, when the actuating bar 12 is moved to the other end of the slot 26, the pins 11 cause the attitude of the pawls 9 to be reversed from the position in FIGS. 3 and 4 to that in FIGS. 5 and 6. In that position the ratchet 7 is permitted to rotate in the direction of the arrow L, but its rotation in the opposite direction is arrested.

The main advantage of the invention arises from the use of the reversible pawls 9 which are complementarily seated in their recesses 8 and are thus able to absorb operating stresses and vibration regardless of the direction of rotation of the ratchet. Also, another advantage results from the use of the actuating pins 11 which, in a simple manner, serve to yieldably bias the pawls into engagement with the ratchet teeth, as well as to shift the pawls from one operating attitude to the other, in terms of direction of ratchet rotation.

WhatIclaim is:

1. In a reversible pawl and ratchet mechanism, the combination of a body defining a ratchet chamber and provided in the periphery of said chamber with at least one pawl-receiving recess in the form of a partial cylinder, a ratchet rotatably mounted in said chamber of said body, a partially cylindrical pawl complemental to and positioned in said recess for partial rotating movement about its own axis, said pawl having a concave surface oriented toward said ratchet and also having a pair of longitudinal edges at opposite sides of said concave surface, said longitudinal edges of said pawl being selectively engageable with teeth of said ratchet as a function of partially rotating the pawl in its recess from one adjusted attitude to another, an actuating disc mounted in said chamber coaxially with said ratchet at one side of the latter, said disc being partially rotatable within limits relative to said body and being provided with a radial cavity, a pin slidable radially in said cavity and having a convex outer end engageable with the concave surface of said pawl whereby partial rotation of said disc relative to said body may partially rotate said pawl in its recess from either of its adjusted attitudes to the other, and means yieldably biasing said pin radially outwardly in said cavity into engagement with said pawl.

2. The mechanism as defined in claim 1 together with an actuating bar secured to said disc and projecting through an arcuate slot in said body, said bar being mova ble within limits of said slot for partially rotating said disc within corresponding limits relative to said body,

said partial rotation of the disc being effective to move said pin across the concave surface of said pawl from either of its longitudinal edges to the other.

3. The mechanism as defined in claim 1 wherein said yieldable biasing means comprise a compression spring positioned in said cavity of said disc and urging said pin radially outwardly against said pawl.

4. The mechanism as defined in claim 1 wherein said yieldable biasing means are constituted by delivery of fluid under pressure into said cavity to urge said pin radially outwardly against said pawl.

5. The mechanism as defined in claim 1 wherein said ratchet includes a journal rotatable in said body and having said disc mounted thereon for independent rotation of the journal and the disc, said journal and said disc being provided with fluid passage means continuously communicating with said disc cavity, and said yieldable biasing means being constituted by delivery of fluid under pressure through said passage means into said cavity to urge said pin radially outwardly against said pawl.

6. The mechanism as defined in claim 5 wherein said fluid passage means include an annular groove provided at the mounting of said disc on said journal, duct means in said journal communicating with said groove for delivering pressurized fluid thereinto, and duct means in said disc communicating said groove with said cavity.

References Cited UNITED STATES PATENTS 1,835,675 12/ 1931 Smith et al. 18882.2 2,312,156 2/1943 Fuehrer 18882.2

FOREIGN PATENTS 111,005 7/ 1940 Australia. 574,953 3/1958 Italy.

ROBERT A. OLEARY, Primary Examiner. WILLIAM E. WAYNER, Assistant Examiner.

U.S. Cl. X.R. 74527, 577 

